In Java(tm), null is not a keyword, but a special literal of the null type. It can be cast to any reference type, but not to any primitive type such as int or boolean. The null literal doesn't necessarily have value zero.
Add a jump rope to the motion and you will be skipping rope. The skipping moves won't bulk you up, but they can tone the muscles in your thighs, calves and butt -- your quadriceps, hamstrings, gluteals, iliopsoas, gastrocnemius and tibialis anterior.
Step 1. Warm up your muscles by stretching before working on your vertical leap or engaging in an activity in which you will be performing jumps. Take a full five minutes to stretch your hamstrings, calves, arms, shoulders, back and neck. Do not neglect any major body parts.tep 1. Warm up your muscles by stretching before working on your vertical leap or engaging in an activity in which you will be performing jumps. Take a full five minutes to stretch your hamstrings, calves, arms, shoulders, back and neck. Do not neglect any major body parts.